Soil Taxonomy And Differentiation Based On Analysis Of Soil Forming Factors In Hubei Province

Along with the rapid development of urbanization and socioeconomy, the contradiction between human and environment resources has become increasingly prominent. As an important part of resources and environment, soil is now facing land degradation problems in quality such as pollution, erosion, decline of soil fertility, and so on, and the amount of soil are drastically reduced due to the infrastructure construction and industrial development in quantity. So how to make rational use of resource and pretect soil environment has received wide attention in recent years. Soil classification is the foundation and basis of decision-making and management of development, utilization and protection of soil resources. Making diagnostic horizons and characteristics as indicators, soil taxonomy with the quantitative features can reflect the inherent properties of soil and the rule of soil formation, and it shows advantages in soil information communication, soil quality assessment and land use planning compare with traditional genetic classification. Therefore it has important significance to conduct research on soil taxonomy and differentiation rule of soils.This paper takes Hubei Province as investigation area, launched the soil taxonomy research, extracted features of soil profile climate, parent material, environmental factors such as topography and physicochemical properties from the existing soil data, soil taxonomy searched one by one, identified diagnostic horizon and diagnostic characteristics, determined the attribution of a single profile in taxonomy, summarized the classification of soil types that Hubei province may possess. According to the relationship between summarized environmental factors combination and soil type distribution, emplaced soil survey points, carried out the soil series survey. Adopts Jianghan Plain in Hubei Province as the typical region, analyzed the relationship between the classification of spatial distribution of soil system and environmental factors; takes Zaoyang as sample area, use the random forest method for soil research cartography automatic classification; selected 3 kinds of zonal soil under different degree of erosion and comparative studied the structure characteristics and permeability the performance. The main results and conclusions are as follows:Utilize the quantitative index of soil taxonomy to collate summarize and taxonomy search the existing soil profile, find out the correct system classification, and establish the relationship between system classification and environmental factors, landscape conditions. According to the analysis of existing soil data and environmental data of Hubei province, it belongs to the typical transition region in the aspects of climate, vegetation and soil, and the main soil forming processes ware humification, anthropic alteration, oxidation-reduction process, iron and aluminum riching, sliming, calcium accumulating, cambic soil layer development and so on. So there were eight orders,such as Anthrosols, Vertosols, Gleyosols, Isohumosols, Ferrosols, Argosols, Cambosols and Primosols in Hubei province, and mainly was Anthrosols, Ferrosols, Argosols and Cambosols.According to the superposition results maps of climate, topography, parent material, land use, etc., divided soil survey series unit, disposed 203 sampling points in Hubei province, according to the soil forming environment and the sample physical and chemical analysis data of profile, diagnostic horizons, for example, anthrostagnic epipedon, humic epipedons, hydragric horizon, LAC-ferrichorizon, argic horizon and cambic horizon, was identified, and diagnostic characteristics such as gleyic features, redox features, lithologic characters, ferric property, calcaric property, lithic contact, anthroturbic layer, ustic/udic/perudic/stagnic/anthrostagnic/aquic/peraquic soil moisture regime, frigid/mesic/thermic were also identified. All the soil profiles were divided into 6 orders,8 subclasses,17 groups and 29 subgroups in total, and 154 soil series was confirmed through profile comparison.The research result of the effect of Jianghan plain soil parent material, topography and human activities on soil properties and soil space distribution evolution shows that: The influence of parent material in its region on soil types is mainly reflected in the soil order, Q4 (Holocene) alluvial, alluvial-Lacustrine sediments parent material mainly formed entisol and cambisols, Q3 (Xiashu loess) parent material generally develop of alfisol; in plain area the topography through control the flow direction and distribution of surface water and groundwater influence the differentiation of soil types, with the change of topography, lower elevation, the underground water level increases gradually close to surface, laws of soil type distribution is:entisol→cambisol→anthrosol→gleisoil; the human activities reclaiming land from lakes, water curing changed the situation of soil moisture and ventilation condition, influenced the natural succession direction of soil, caused the entisol, cambisols and gleisoil, etc. natural soil types change to anthrosol, human irrational reclamation will lead to soil return potential and secondary incubation, make the soil produce reverse succession. The Chinese soil classification system can reflect the spatial variability of parent material, topography, human’s activity etc. factors and the law of soil type distribution well, and provides practical examples for further perfecting the soil taxonomy.Taking Zaoyang city as sample region, selected 9 topographical factors:Altitude, slope, aspect, curvature, mean curvature, along the profile curvature, along the contour curvature, catchment area (CA), specific catchment area (SCA), compound topographic index (CTI),2 vegetation factor:mean NDVI (normalized differential vegetation index) and maximum NDVI,3 climate factors:years the average temperature, rainfall, evapotranspiration, and soil parent material factor, and use Arcgis software space analysis function extract the above 15 factors as predictor variables, adopted random forests method established the relationship model between 17 soil series and environment factors in the study region, inference digital soil map from obtained relationship. Compared the established confusion matrix with the original soil map, the Kappa coefficient is 0.59, it is proved that the predicted results and the actual is of medium consistency, indicated that the soil distribution map of soil is consistent with the actual in the study region. The study also shows that the importance sequence environmental factors of Zaoyang city soil formation are topography (elevation), climate (rainfall, evaporation), parent material, is conducive to the understanding process of soil in the study region. The method based on obtaining the relationship between soil and environment from the original soil map by random forest, accordingly mapping digital soil, compared with the traditional mapping methods, improved work efficiency, it can establish the relationship between environmental factors and soil types in the unknown regions, it can be used as the premise of soil survey.Three different soil erosion degrees (feeble, light, moderate and heavy) of 3 typical types of zonal soils (ustic argosols, udic argosols and udic ferrosols) of Hubei province was selected as research objects, through determination and analysis of soil saturated hydraulic conductivity, water stable aggregates, porosity composition and other physical and chemical properties, investigated the change and its main influencing factors of zonal soil structures in different erosion degrees. The results show that:free iron and aluminum oxides (Fed and Ald) content sequence is udic ferrosols> ustic argosols> udic argosols. Furthermore, the free iron and aluminum oxide have significant difference (P<0.05) for soil erosion degrees; the sequence of mechanical stability and water stability of the three zonal soils is udic ferrosols> ustic argosols> udic argosols, and water stability MWD, GMD of soil aggregates decreases gradually with the increase of the erosion degree; saturated hydraulic conductivity sequence is udic ferrosols> ustic argosols> udic argosols, which shows decreasing trend with the increasing of erosion degree, of which the saturated hydraulic conductivity of feeble soil erosion is higher than other soils. From what has been discussed above we can conclude that free iron and aluminum oxides are the main dominate factors affect stability of zonal soil structure stability in Hubei province.